The Tory MP who defected to the Lib Dems has claimed his decision to cross the floor was sparked by Jacob Rees-Mogg's treatment of a former health adviser.
Dr Philip Lee dramatically resigned from the Conservatives on Tuesday, wiping out Prime Minister Boris Johnson’s slim majority.
Speaking to Eddie Mair on LBC Radio about his decision to quit, the MP for Bracknell said the “disdain and disrespect” Jacob Rees-Mogg had shown to Dr David Nicholl had tipped him over the edge.
Dr Nicholl, who wrote part of the Operation Yellowhammer no-deal mitigation report, was accused of "fearmongering" on Mr Rees-Mogg’s radio show yesterday.
The former government adviser expressed concern about a possibly rising mortality rate in the event of a no-deal Brexit.
But Mr Rees-Mogg said his argument was "the worst excess of Project Fear" adding that the doctor should be "quite ashamed".
Speaking about the confrontation on Tuesday evening Dr Lee said: “You can say it in a posh voice but if it’s BS, it’s BS.”
Dr Lee, a qualified doctor who has worked as a GP for the past 15 years, criticised the government in a statement on Thursday evening.
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He accused Mr Johnson’s administration of "manipulation, bullying and lies" to achieve a damaging Brexit that is "putting lives at risk".
"The Party I joined in 1992 is not the Party I am leaving today," he added.
“This Conservative Government is aggressively pursuing a damaging Brexit in unprincipled ways.”
The Prime Minister has signalled he will try to call a snap general election if he is defeated by the cross-party alliance’s bid to take control of the Commons agenda and pass legislation which would prevent a no-deal Brexit on October 31.
The move would require the Prime Minister to seek a delay to Brexit until January 31, 2020 if no agreement has been reached and MPs have not approved a no-deal withdrawal.
Mr Johnson told MPs the legislation aimed at blocking a no-deal Brexit would “force me to go to Brussels and beg an extension” and “destroy any chance” of negotiating an agreement.
Labour leader Jeremy Corbyn said Mr Johnson was leading a Government with “no mandate, no morals and, as of today, no majority”.
In a sign of the bitter divisions within the Conservative ranks, former chancellor Philip Hammond accused Downing Street of “rank hypocrisy” and warned of the “fight of a lifetime” if officials attempt to prevent him from standing at the next general election as a Conservative candidate.
Mr Johnson told rebel MPs on Tuesday that a delay to Brexit would be an “extinction-level event”, a Government spokesman said.
“I think this Prime Minister has been clear, and in fact I heard him say it in the meeting with the rebels today, that an extension for politicians of all sorts is an extinction-level event. It would undermine democracy and faith in democracy.”